1. Field
The present disclosure relates to the field of Web Service (WS) technology, and more particularly relates to a method and system for property-based indexing and querying of distributed WS resources (WS-Resources) in multiple loosely coupled WS-ServiceGroups.
2. General Background
The WS technology enables application programs to communicate with each other in a manner independent of platforms and programming languages. WS technology is the technical basis of Service Oriented Architecture (SOA). The SOA is a component model which connects different functional elements (also referred to as services) of application programs by defining interfaces and contracts between these services. An interface is typically defined in a neutral way, i.e., not being forced to bind to a specific implementation. Accordingly, a neutral interface is often referred to as a loose coupling of services.
A WS is a software interface that describes a set of operations in which access is passed in standardized Extensible Markup Language (XML) messages over a network. A WS uses XML language-based protocols to describe operations to be executed or data to be exchanged with another WS.
A WS-Resource Architecture has been proposed as a method to represent the relationship between stateful resources and WS's. Until recently, several standards have been defined to address complex problems related to querying and accessing Web Services.
In general, a WS-Resource Framework (WSRF) defines a set of mechanisms for WS-Resources, WS-ResourceProperties and WS-ServiceGroups.
The WSRF defines the standardized description of WS-Resource methods according to specific WS message exchanges and related XML definitions. The WS-Resource Framework allows WS-Resources to be declared, created, accessed, monitored for changes, and destroyed via conventional WS mechanisms, but does not require that WS components of WS-Resources that provide access to the associated stateful resources be implemented as a stateful resource processor.
A WS-Resource is a Web service through which a resource can be accessed. The WS-Resource is further defined as follows: (1) an identifier of the resource must appear as a part of any message directed to the WS-Resource, to allow the WS-Resource to build the semantic interpretation of the resource targeted by the message; (2) the set of properties of the resource must be expressed using an XML Infoset described by XML schemas.
A WS-Resource Property is information defined as a part of a state model of a WS-Resource, and may reflect state, metadata, manageability information and the like of the resource.
A WS ServiceGroup (hereinafter ServiceGroup) is a WS-Resource, which represents a collection of Web services or WS-Resources and the information that pertains to them. The purpose of the group is application domain specific.
The WS-Resource Framework is mainly defined by five standardized specifications, which are a shown in the following Table 1.
TABLE 1NameDescriptionWS-ResourceLifetimeMechanisms for WS-Resource destruction,including message exchanges that allow arequestor to destroy a WS-Resource, eitherimmediately or by using a time-basedscheduled resource termination mechanism.WS-ResourcePropertiesDefinition of a WS-Resource, andmechanisms for retrieving, changing, anddeleting WS-Resource properties.WS-RenewableReferencesA conventional decoration of a WS-Addressing endpoint reference with policyinformation needed to retrieve an updatedversion of an endpoint reference whenit becomes invalid.WS-ServiceGroupAn interface to heterogeneous by-referencecollections of Web services.WS-BaseFaultsA base fault XML type for use whenreturning faults in a Web services messageexchange.
In addition, a family of WS-Notifications (WSN) specifications, which is used to define standard flows for creating an event-driving system in a Web services environment, has been proposed. The family of WS-Notification specifications defines a general, topic-based Web service system, which is used to publish/subscribe WSRF-based interactions. One basic method employed is to define mechanisms and interfaces to allow a client to subscribe interested topics, such as any change of resource property values of a WS-Resource. For example, the family of specifications related to the WS-Resource Framework and WS-Notification described above is available at www.oasis-open.org. In the WS-Resource Framework, only the resource description framework and client/server mode are defined for the client to get and set the properties of the WS-Resources. Therefore, when there is more than one ServiceGroup, the client queries all the instances of the ServiceGroups to get the properties of the WS-Resources. Currently, there is no better way to integrate multiple ServiceGroups so that the client can query properties of all the distributed target WS-Resources.